Transmitter



W. G. HOUSKEEPER.

TRANSMITTER.

APPLICATION FILED MAR. 25, 1918.

328,996, Patented J an. 27, 1920.

' varying light. The resistance with the UNITED. srA'rEs PATENT OFFICE.

WILLIAM G, HOUSKEEPER, 0F PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A

CORPORATION OF NEW YORK.

TRANSMITTER.

To all whom it may concern.

Be it known that I, WILLIAM G. Hoos- KEEPER, a citizen of the United States, residing at Philadelphia, in the county of Philadelphia, State of Pennsylvania, have invented certain new and useful Improvements in Transmitters, of which the following is a full, clear, concise, and exact description.

This invention relates'in general to transmitters and more particularly to a telephone transmitter employing selenium as the -ma terial which varies inresistance with the varying pressure resulting from vibration of the transmitter diaphragm.

Selenium exists in various forms, in some of which it is non-conducting, but in the metallic crystalline state it is not only conducting but'in addition it has the property of varying in conductivity when exposed to varying pressures or to the influence of property of varying in infiuenceof light has long been taken advantage of for various purposes, but the' variation in resistance with varying pressure has not been made use of, largely because of the difliculty of obtaining satisfactory and uniform results with the crystals heretofore obtainable, these crystals being microscopic in size. Recently, however, as mentioned in Brown Patent No. 1,219,432 of March 20, 1917, it has been found possible to'produce selenium crystals of considerable size by sublimation of selenium vapor either in a high vacuum or at atmospheric pressure. Crystals obtained in this manner can be handled to give uniformresults and are found to vary considerably in resistance with a moderate variation in pressure. Therefore, in accordance with this invention, there is provided a transmitter in which one or more selenium crystals are used as the substance changing in resistance with the changing pressure resulting from the impinging of the sound waves upon the transmitter diaphragm.

In the accompanying drawing, Figure 1 is a view, partially in section, of a familiar type of transmitter in which a selenium crystal is employed in place. of a platinum contact point; and Fig. 2 illustrates a modification proposed for use when it is advan- Specification of Letters Patent.

. tageous to e Patented Jan. 27, 1920.

Application filed March 25, 1918. Serial No. 224,509.

ploy a larger number of crystals. I

Referring now to Fig. 1, the containing casing v5 is beveled as shown to provide the conical mouthpiece 6, back of which is mounted the diaphragm 7. This diaphragm, which is provided at its perimeter with a soft rubber cushion 8, is seated in the metal ring 9. Secured to the boss 10 by means of the flexible reed 11 is the support 12, upon which are mounted the spring members 13 and 14, insulated from each other and the support by means of hard rubber bushings and washers 1515. Securely fastened in the free end of spring 13 is the selenium crystal 16 engaged at either side by the carbon plates 19 and 20, the

former of which is securedto the central portion of the diaphragm 7 and the latter to the free end of spring 14. While carbon is to be preferred as the material for these plates, any other material, which does not affect the selenium chemically, may be used in its place. An adjusting screw 21 is adapted to engage the-beveled portion 22, of support '12 and provide a suitable means for adjustment of the contact pressures. This transmitter is adapted to be connected into the circuit so that current passes from spring 14 through carbon plate 20, selenium crystal 16 and carbon plate 19. Thus vibrations of the diaphragm 7 cause varying pressures upon the crystal 16 which result in corresponding changes in resistance and consequently make possible the -convers1on"o f the sound waves impinging upon the diaphragm into fluctuatlng voice currents which may be transmitted over a l1ne to actuate a suitable receiving device at the opposite end.

In Fig. 2 is illustrated a modification employing a transmitter button having a cup member 25 in which are mounted the back electrode 26 and the front electrode 27 the intervening space being filled with selenium crystals. The front electrode is secured to the mica disk 28 which in turn 1s rigidly secured to the transmitter diaphragm 29. The back electrode is secured to the shank 30 which is rigidly secured to the bridge member (not shown on the drawing) so that vibrations of the diaphragm 29 result in,

What is claimed is: I 1. In a transmitter, a variable resistance element composed of selenium adapted to 1 vary in resistance with varlation in pressure.

2. In a transmitter, a variable resistance element composed of selenium, and a dia- 10 phragm adapted upon vibration to vary the pressure upon the resistance member.

3. In a transmitter, a variable resistance element composed of one or more selenium --crystals adapted to vary in resistance With variation in pressure.

4. In a transmitter, a diaphragm, a variable resistance element. composed of selenium, and means for maintaining said resistance element in engagement With said diaphragm.

In witness whereof I hereunto subscribe my name this 20th day of March A. D., 191s.

WILLIA G. 'HOUSKEEPER. 

